Value-pluralism is commonly held to support liberal political morality. This is argued by John Rawls and his school and, more instructively, by Isaiah Berlin and Joseph Raz. Against this common view it is argued that a strong version of value-pluralism and liberalism are incompatible doctrines. Some varieties of ethical pluralism are distinguished, and the claim of value-incommensurability made by strong pluralism is elucidated. The argument that liberal political morality consists of principles of right that are unaffected by the truth of strong pluralism is examined and rejected. Strong pluralism is understood as the view that some goods and bads are rationally incommensurable. It is argued that if strong value-pluralism is true, then liberal political morality cannot be defended. Neither negative liberty nor individual autonomy can have general priority if it is true that the central goods specified by liberal political morality are incommensurables. This difficulty is not avoided by liberal theories that do not demand the maximization of a single value such as liberty. If strong pluralism is true, then liberal institutions are not a standard of legitimacy by reference to which all regimes are to be assessed. They are merely one variety of modus vivendi . Liberal institutions have no universal legitimacy. Yet liberal cultures are partly constituted by a belief in the universal authority of the principles which inform their practices and institutions. This belief strong pluralism subverts. Value-pluralism and liberalism are rival doctrines. The political implication of strong pluralism is not liberalism but modus vivendi . Sometimes modus vivendi is best fostered by liberal institutions. Sometimes it is best fostered by non-liberal institutions. Where the latter is true, liberals and pluralists part company